WASHINGTON (AP) _ Nursing home residents, their advocates and state officials accused a government agency on Thursday of trying to enforce nursing home reforms before it even spelled out how those institutions could comply with the new rules.

They said the Health Care Finance Administration put the cart before the horse by issuing rules for enforcement of a 1987 reform law without providing necessary guidelines for complying.

''We simply have been astounded by HCFA's delays in providing education, information and guidance to the states on the important, most timely, provisions of the law,'' Susan Rourke, president of the National Citizens' Coalition for Nursing Home Reform, told the Senate Special Committee on Aging.

''It is a very difficult position for the states to be in required by law to implement a program without regulatory guidance and the probability that whatever we do may not be what the regulations ultimately require,'' said Dana Petrowsky, administrator of the Division of Health Facilities in Iowa's Department of Inspections and Appeals.

The Omnibus Budget Reconciliation Act of 1987 obligated the Department of Health and Human Services through HCFA to set standards for quality of care, provide for protection of patients' rights, and ensure minimum training of nurse's aides, who provide most patient care in nursing homes.

The legislation provided that the reforms be phased in over 2 1/2 years.

Experts in caring for the elderly said state agencies and health care providers responsible for implementing the reforms have not received from HCFA regulations for two major aspects of the legislation - nurse's aide training and evaluation and client preadmission screening.

Meanwhile HCFA issued final rules regarding nursing home survey and certification requirements, including the inspection system to be used, in February.

C. Ross Anthony, associate administrator for program development at HCFA, said much of the work to establish the standards had been done before the reform law was passed so his agency decided to proceed with enforcement regulations.

''We did not want to delay such important areas of reform as enhanced residents rights and strengthened quality of care,'' he said.

G. Janet Tulloch, a resident of a Washington, D.C. nursing home, said enactment of the law ''meant light at the end of a very dark tunnel of subtle abuse.''

But the waivers of nursing aide training and on-site nurses requirements permitted under the rules HCFA propounded in February ''will allow the easiest solution wherever possible'' said the 65-year-old woman whose cerebal palsy has forced her to live in a nursing home for 21 years.

Congress wrote unusually detailed deadlines into the law because of efforts by the Reagan administration to reduce federal regulation of nursing homes despite widespread reports of abuse and corruption.

Sen. David Pryor, D-Ark., the committee chairman, questioned whether the action by HCFA in issuing enforcement rules before it issued guidelines was ''a back door attempt by HCFA to deregulate nursing homes.''